go example_textvar_test 源码
golang example_textvar_test 代码
文件路径：/src/flag/example_textvar_test.go
// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package flag_test
import (
"flag"
"fmt"
"net"
"os"
)
func ExampleTextVar() {
fs := flag.NewFlagSet("ExampleTextVar", flag.ContinueOnError)
fs.SetOutput(os.Stdout)
var ip net.IP
fs.TextVar(&ip, "ip", net.IPv4(192, 168, 0, 100), "`IP address` to parse")
fs.Parse([]string{"-ip", "127.0.0.1"})
fmt.Printf("{ip: %v}\n\n", ip)
// 256 is not a valid IPv4 component
ip = nil
fs.Parse([]string{"-ip", "256.0.0.1"})
fmt.Printf("{ip: %v}\n\n", ip)
// Output:
// {ip: 127.0.0.1}
//
// invalid value "256.0.0.1" for flag -ip: invalid IP address: 256.0.0.1
// Usage of ExampleTextVar:
// -ip IP address
// IP address to parse (default 192.168.0.100)
// {ip: <nil>}
}
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